Expandable roller reamer

ABSTRACT

An expandable downhole tool for use in a drilling assembly positioned within a wellbore includes a tool body having an axial flowbore extending therethrough and a moveable arm. The moveable arm includes a roller structure including cutters and rotatably mounted on the moveable arm. The moveable arm is configured to move outwardly in response to actuation of the expandable downhole tool.

BACKGROUND OF INVENTION

1. Field of the Invention

The present disclosure relates to a roller reamer for stabilizing adrillstring and reducing torque.

2. Description of the Related Art

In the drilling of oil and gas wells, concentric casing strings areinstalled and cemented in the borehole as drilling progresses toincreasing depths. Each new casing string is supported within thepreviously installed casing string, thereby limiting the annular areaavailable for the cementing operation. Further, as successively smallerdiameter casing strings are suspended, the flow area for the productionof oil and gas is reduced. Therefore, to increase the annular space forthe cementing operation, and to increase the production flow area, it isoften desirable to enlarge the borehole below the terminal end of thepreviously cased borehole. By enlarging the borehole, a larger annulararea is provided for subsequently installing and cementing a largercasing string than would have been possible otherwise. Accordingly, byenlarging the borehole below the previously cased borehole, the bottomof the formation can be reached with comparatively larger diametercasing, thereby providing more flow area for the production of oil andgas.

Various methods have been devised for passing a drilling assemblythrough an existing cased borehole and enlarging the borehole below thecasing. One such method is the use of an underreamer, which hasbasically two operative states—a closed or collapsed state, where thediameter of the tool is sufficiently small to allow the tool to passthrough the existing cased borehole, and an open or partly expandedstate, where one or more arms with cutters on the ends thereof extendfrom the body of the tool. In this latter position, the underreamerenlarges the borehole diameter as the tool is rotated and lowered in theborehole.

A “drilling type” underreamer is typically used in conjunction with aconventional pilot drill bit positioned below or downstream of theunderreamer. The pilot bit can drill the borehole at the same time asthe underreamer enlarges the borehole formed by the bit. Underreamers ofthis type usually have hinged arms with roller cone cutters attachedthereto. Most of the prior art underreamers utilize swing out cutterarms that are pivoted at an end opposite the cutting end of the cuttingarms, and the cutter arms are actuated by mechanical or hydraulic forcesacting on the arms to extend or retract them. Typical examples of thesetypes of underreamers are found in U.S. Pat. Nos. 3,224,507; 3,425,500and 4,055,226. In some designs, these pivoted arms tend to break duringthe drilling operation and must be removed or “fished” out of theborehole before the drilling operation can continue. The traditionalunderreamer tool typically has rotary cutter pocket recesses formed inthe body for storing the retracted arms and roller cone cutters when thetool is in a closed state. The pocket recesses form large cavities inthe underreamer body, which requires the removal of the structural metalforming the body, thereby compromising the strength and the hydrauliccapacity of the underreamer. Accordingly, these prior art underreamersmay not be capable of underreaming harder rock formations, or may haveunacceptably slow rates of penetration, and they are not optimized forthe high fluid flow rates required. The pocket recesses also tend tofill with debris from the drilling operation, which hinders collapsingof the arms. If the arms do not fully collapse, the drill string mayeasily hang up in the borehole when an attempt is made to remove thestring from the borehole.

Conventional underreamers have several disadvantages, including cuttingstructures that are typically formed of sections of drill bits ratherthan being specifically designed for the underreaming function.Therefore, the cutting structures of most underreamers do not reliablyunderream the borehole to the desired diameter. A further disadvantageis that adjusting the expanded diameter of a conventional underreamerrequires replacement of the cutting arms with larger or smaller arms, orreplacement of other components of the underreamer tool. It may even benecessary to replace the underreamer altogether with one that provides adifferent expanded diameter. Another disadvantage is that manyunderreamers are designed to automatically expand when drilling fluid ispumped through the drill string, and no indication is provided at thesurface that the underreamer is in the fully-expanded position. In someapplications, it may be desirable for the operator to control when theunderreamer expands.

Accordingly, it would be advantageous to provide an underreamer that isstronger than prior art underreamers, with a hydraulic capacity that isoptimized for the high flow rate drilling environment. It would furtherbe advantageous for such an underreamer to include several designfeatures, namely cutting structures designed for the underreamingfunction, mechanisms for adjustment of the expanded diameter withoutrequiring component changes, and the ability to provide indication atthe surface when the underreamer is in the fully-expanded position.Moreover, in the presence of hydraulic pressure in the drill string, itwould be advantageous to provide an underreamer that is selectivelyexpandable.

Another method for enlarging a borehole below a previously casedborehole section includes using a winged reamer behind a conventionaldrill bit. In such an assembly, a conventional pilot drill bit isdisposed at the lowermost end of the drilling assembly with a wingedreamer disposed at some distance behind the drill bit. The winged reamergenerally comprises a tubular body with one or more longitudinallyextending “wings” or blades projecting radially outwardly from thetubular body. Once the winged reamer has passed through any casedportions of the wellbore, the pilot bit rotates about the centerline ofthe drilling axis to drill a lower borehole on center in the desiredtrajectory of the well path, while the eccentric winged reamer followsthe pilot bit and engages the formation to enlarge the pilot borehole tothe desired diameter.

Yet another method for enlarging a borehole below a previously casedborehole section includes using a bi-center bit, which is a one-piecedrilling structure that provides a combination underreamer and pilotbit. The pilot bit is disposed on the lowermost end of the drillingassembly, and the eccentric underreamer bit is disposed slightly abovethe pilot bit. Once the bi-center bit has passed through any casedportions of the wellbore, the pilot bit rotates about the centerline ofthe drilling axis and drills a pilot borehole on center in the desiredtrajectory of the well path, while the eccentric underreamer bit followsthe pilot bit and engages the formation to enlarge the pilot borehole tothe desired diameter. The diameter of the pilot bit is made as large aspossible for stability while still being capable of passing through thecased borehole. Examples of bi-center bits may be found in U.S. Pat.Nos. 6,039,131 and 6,269,893.

As described above, winged reamers and bi-center bits each includeunderreamer portions that are eccentric. A number of disadvantages areassociated with this design. First, before drilling can continue, cementand float equipment at the bottom of the lowermost casing string must bedrilled out. However, the pass-through diameter of the drilling assemblyat the eccentric underreamer portion barely fits within the lowermostcasing string. Therefore, off-center drilling is required to drill outthe cement and float equipment to ensure that the eccentric underreamerportions do not damage the casing. Accordingly, it is desirable toprovide an underreamer that collapses while the drilling assembly is inthe casing and that expands to underream the previously drilled boreholeto the desired diameter below the casing.

Further, due to directional tendency problems, these eccentricunderreamer portions have difficulty reliably underreaming the boreholeto the desired diameter. With respect to a bi-center bit, the eccentricunderreamer bit tends to cause the pilot bit to wobble and undesirablydeviate off center, thereby pushing the pilot bit away from thepreferred trajectory of drilling the well path. A similar problem isexperienced with respect to winged reamers, which only underream theborehole to the desired diameter if the pilot bit remains centralized inthe borehole during drilling. Accordingly, it is desirable to provide anunderreamer that remains concentrically disposed in the borehole whileunderreaming the previously drilled borehole to the desired diameter.

In drilling operations, it is conventional to employ a tool known as a“stabilizer.” In standard boreholes, traditional stabilizers are locatedin the drilling assembly behind the drill bit for controlling thetrajectory of the drill bit as drilling progresses. Traditionalstabilizers control drilling in a desired direction, whether thedirection is along a straight borehole or a deviated borehole.

In a conventional rotary drilling assembly, a drill bit may be mountedonto a lower stabilizer, which is disposed approximately 5 feet abovethe bit. Typically the lower stabilizer is a fixed blade stabilizer thatincludes a plurality of concentric blades extending radially outwardlyand spaced azimuthally around the circumference of the stabilizerhousing. The outer edges of the blades are adapted to contact the wallof the existing cased borehole, thereby defining the maximum stabilizerdiameter that will pass through the casing. A plurality of drill collarsextends between the lower stabilizer and other stabilizers in thedrilling assembly. An upper stabilizer is typically positioned in thedrill string approximately 30-60 feet above the lower stabilizer. Therecould also be additional stabilizers above the upper stabilizer. Theupper stabilizer may be either a fixed blade stabilizer or, morerecently, an adjustable blade stabilizer that allows the blades to becollapsed into the housing as the drilling assembly passes through thecasing and then expanded in the borehole below. One type of adjustableconcentric stabilizer is manufactured by Andergauge U.S.A., Inc.,Spring, Tex. and is described in U.S. Pat. No. 4,848,490. Another typeof adjustable concentric stabilizer is manufactured by Halliburton,Houston, Tex. and is described in U.S. Pat. Nos. 5,318,137; 5,318,138;and 5,332,048.

In operation, if only the lower stabilizer was provided, a “fulcrum”type assembly would be present because the lower stabilizer acts as afulcrum or pivot point for the bit. Namely, as drilling progresses in adeviated borehole, for example, the weight of the drill collars behindthe lower stabilizer forces the stabilizer to push against the lowerside of the borehole, thereby creating a fulcrum or pivot point for thedrill bit. Accordingly, the drill bit tends to be lifted upwardly at anangle, i.e. build angle. Therefore, a second stabilizer is provided tooffset the fulcrum effect. Namely, as the drill bit builds angle due tothe fulcrum effect created by the lower stabilizer, the upper stabilizerengages the lower side of the borehole, thereby causing the longitudinalaxis of the bit to pivot downwardly so as to drop angle. A radial changeof the blades of the upper stabilizer can control the pivoting of thebit on the lower stabilizer, thereby providing a two-dimensional,gravity based steerable system to control the build or drop angle of thedrilled borehole as desired.

When an underreamer or a winged reamer tool is operating behind aconventional bit to underream the borehole, that tool provides the samefulcrum effect to the bit as the lower stabilizer in a standardborehole. Similarly, when underreaming a borehole with a bi-center bit,the eccentric underreamer bit provides the same fulcrum effect as thelower stabilizer in a standard borehole. Accordingly, in a drillingassembly employing an underreamer, winged reamer, or a bi-center bit, alower stabilizer is not typically provided. However, to offset thefulcrum effect imparted by to the drill bit, it would be advantageous toprovide an upper stabilizer capable of controlling the inclination ofthe drilling assembly in the underreamed section of borehole.

In particular, it would be advantageous to provide an upper stabilizerthat engages the wall of the underreamed borehole to keep the centerlineof the pilot bit centered within the borehole. When utilized with aneccentric underreamer that tends to force the pilot bit off center, thestabilizer blades would preferably engage the opposite side of theexpanded borehole to counter that force and keep the pilot bit oncenter.

SUMMARY OF THE INVENTION

In one aspect, embodiments disclosed herein relate to an expandabledownhole tool for use in a drilling assembly positioned within awellbore. The expandable downhole tool includes a tool body having anaxial flowbore extending therethrough and a moveable arm. The moveablearm includes a roller structure including cutters and rotatably mountedon the moveable arm. The moveable arm is configured to move outwardly inresponse to actuation of the expandable downhole tool.

In another aspect, embodiments disclosed herein relate to a moveable armfor an expandable downhole tool. The moveable arm includes a body, aroller structure including cutters and rotatably mounted on the body.The moveable arm is configured be moveably received into a tool body ofthe expandable downhole tool.

In another aspect, embodiments disclosed herein relate to a method ofunderreaming a wellbore to form an enlarged borehole. The methodincludes using a drill bit to drill the wellbore, disposing anexpandable underreamer above the drill bit, using the expandableunderreamer to enlarge the borehole, and disposing an expandable rollerreamer above the first expandable underreamer, wherein the expandableroller reamer comprises a moveable arm comprising a roller structurecomprising cutters and rotatably mounted on the moveable arm. The methodfurther includes actuating the expandable roller reamer such that thecutters disposed on the roller structure contact the enlarged borehole.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic, cross-sectional view of a drilling assembly;

FIG. 2 is a schematic, cross-sectional view of another drillingassembly;

FIG. 3 is a schematic, cross-sectional view of another drillingassembly;

FIG. 4 is a cross-sectional elevation view of one embodiment of theexpandable tool of the present invention, showing the moveable arms inthe collapsed position;

FIG. 5 is a cross-sectional elevation view of the expandable tool ofFIG. 4, showing the moveable arms in the expanded position;

FIG. 6 is a perspective view of a “blank” arm for the expandable tool ofFIG. 4;

FIG. 7 is a top view of an exemplary arm for the expandable tool of FIG.4 including a wear pad and cutting structures for back reaming andunderreaming;

FIG. 8 is a side elevation view of the arm of FIG. 7;

FIG. 9 is a perspective view of the arm of FIG. 7;

FIG. 10 is a perspective view of the drive ring of the expandable toolof FIG. 4;

FIG. 11 is a cross-sectional elevation view of an alternative embodimentof the expandable tool of the present invention, showing the moveablearms in the collapsed position; and

FIG. 12 is a cross-sectional elevation view of the alternativeembodiment of FIG. 11, showing the moveable arms in the expandedposition.

FIG. 13 is a perspective view of an embodiment of a moveable arm havinga roller reamer structure.

FIGS. 14 a-c are a perspective view of an embodiment of a moveable armhaving a roller reamer structure.

DETAILED DESCRIPTION

The present disclosure relates to a roller reamer for stabilizing adrillstring and reducing torque. The present invention is susceptible toembodiments of different forms. There are shown in the drawings, andherein will be described in detail, specific embodiments of the presentinvention with the understanding that the disclosure is to be consideredan exemplification of the principles of the invention, and is notintended to limit the invention to that illustrated and describedherein.

In particular, various embodiments of the present invention provide anumber of different constructions and methods of operation. Each of thevarious embodiments of the present invention may be used to enlarge aborehole, or to provide stabilization in a previously enlarged borehole,or in a borehole that is simultaneously being enlarged. The embodimentsof the expandable tool of the present invention may be utilized as anunderreamer, or as a stabilizer behind a bi-center bit, or as astabilizer behind a winged reamer or underreamer following aconventional bit. The embodiments of the present invention also providea plurality of methods for use in a drilling assembly. It is to be fullyrecognized that the different teachings of the embodiments disclosedherein may be employed separately or in any suitable combination toproduce desired results.

It should be appreciated that the expandable tool described with respectto the Figures that follow may be used in many different drillingassemblies. The following exemplary systems provide only some of therepresentative assemblies within which the present invention may beused, but these should not be considered the only assemblies. Inparticular, the embodiments of the expandable tool of the presentinvention may be used in any assembly requiring an expandableunderreamer and/or stabilizer for use in controlling the directionaltendencies of a drilling assembly in an expanded borehole.

FIGS. 1-3 show various exemplary drilling assemblies within whichembodiments of the present invention may be utilized. Referringinitially to FIG. 1, a section of a drilling assembly generallydesignated as 100 is shown drilling into the bottom of a formation 10with a conventional drill bit 110 followed by an underreamer 120.Separated from the underreamer 120 by one or more drill collars 130 is astabilizer 150 that controls the directional tendencies of the drillingassembly 100 in the underreamed borehole 25. This section of thedrilling assembly 100 is shown at the bottom of formation 10 drilling aborehole 20 with the conventional drill bit 110, while the underreamercutting arms 125 are simultaneously opening a larger diameter borehole25 above. The drilling assembly 100 is operating below any casedportions of the well.

As described previously, the underreamer 120 tends to provide a fulcrumor pivot effect to the drill bit 110, thereby requiring a stabilizer 150to offset this effect. In the drilling assembly 100, various embodimentsof the expandable tool of the present invention are provided in thepositions of both the underreamer 120 and the stabilizer 150. In oneembodiment, the stabilizer 150 would also include cutting structures toensure that the larger borehole 25 is enlarged to the proper diameter.However, any conventional underreamer may alternatively be utilized withone embodiment of the present invention provided in the position ofstabilizer 150 in the drilling assembly 100. Further, one embodiment ofthe present invention may be utilized in the position of underreamer120, and a conventional stabilizer may be utilized in the position ofstabilizer 150.

Referring now to FIG. 2, where like numerals represent like components,a drilling assembly 200 is shown disposed within formation 10, below anycased sections of the well. The drilling assembly 200 is drilling aborehole 20 utilizing a conventional drill bit 110 followed by a wingedreamer 220. The winged reamer 220 may be separated from the drill bit110 by one or more drill collars 130, but preferably the winged reamer220 is connected directly above the drill bit 110. Upstream of thewinged reamer 220, separated by one or more drill collars 130, is astabilizer 150 that controls the directional tendencies of the drillingassembly 200 in the underreamed borehole 25. The drill bit 110 is shownat the bottom of the formation 10 drilling a borehole 20, while the wingcomponent 225 of the winged reamer 220 is simultaneously opening alarger diameter borehole 25 above. In the assembly 200, one embodimentof the present invention would be located in the position of stabilizer150. In one embodiment of assembly 200, the stabilizer 150 would alsoinclude cutting structures to ensure that the larger borehole 25 isenlarged to the proper diameter.

Referring to FIG. 3, where like numerals represent like components,again a drilling assembly 300 is shown disposed within formation 10,below any cased sections of the well. The drilling assembly 300 utilizesa bi-center bit 320 that includes a pilot bit 310 and an eccentricunderreamer bit 325. As the pilot bit 310 drills the borehole 20, theeccentric underreamer bit 325 opens a larger diameter borehole 25 above.The bi-center bit 320 is separated by one or more drill collars 130 froma stabilizer 150 designed to control the directional tendencies of thebi-center bit 320 in the underreamed borehole 25. Again, the function ofthe stabilizer 150 is to offset the fulcrum or pivot effect created bythe eccentric underreamer bit 325 to ensure that the pilot bit 310 stayscentered as it drills the borehole 20. In one embodiment of the drillingassembly 300, one embodiment of the expandable tool of the presentinvention would be located in the position of stabilizer 150. In anotherembodiment of assembly 300, the stabilizer 150 would also includecutting structures to ensure that the larger borehole 25 is enlarged tothe proper diameter.

Referring now to FIGS. 4 and 5, one embodiment of the expandable tool ofthe present invention, generally designated as 500, is shown in acollapsed position in FIG. 4 and in an expanded position in FIG. 5. Theexpandable tool 500 comprises a generally cylindrical tool body 510 witha flowbore 508 extending therethrough. The tool body 510 includes upper514 and lower 512 connection portions for connecting the tool 500 into adrilling assembly. In approximately the axial center of the tool body510, one or more pocket recesses 516 are formed in the body 510 andspaced apart azimuthally around the circumference of the body 510. Theone or more recesses 516 accommodate the axial movement of severalcomponents of the tool 500 that move up or down within the pocketrecesses 516, including one or more moveable, non-pivotable tool arms520. Each recess 516 stores one moveable arm 520 in the collapsedposition. In one embodiment, the expandable tool includes three moveablearms 520 disposed within three pocket recesses 516. In the discussionthat follows, the one or more recesses 516 and the one or more arms 520may be referred to in the plural form, i.e. recesses 516 and arms 520.Nevertheless, it should be appreciated that the scope of the presentinvention also comprises one recess 516 and one arm 520.

The recesses 516 further include angled channels 518 that provide adrive mechanism for the moveable tool arms 520 to move axially upwardlyand radially outwardly into the expanded position of FIG. 5. A biasingspring 540 may be included to bias the arms 520 to the collapsedposition of FIG. 4. The biasing spring 540 is disposed within a springcavity 545 and covered by a spring retainer 550. Retainer 550 is lockedin position by an upper cap 555. A stop ring 544 is provided at thelower end of spring 540 to keep the spring 540 in position.

Below the moveable arms 520, a drive ring 570 is provided that includesone or more nozzles 575. An actuating piston 530 that forms a pistoncavity 535, engages the drive ring 570. A drive ring block 572 connectsthe piston 530 to the drive ring 570 via bolt 574. The piston 530 isadapted to move axially in the pocket recesses 516. A lower cap 580provides a lower stop for the axial movement of the piston 530. An innermandrel 560 is the innermost component within the tool 500, and itslidingly engages a lower retainer 590 at 592. The lower retainer 590includes ports 595 that allow drilling fluid to flow from the flowbore508 into the piston chamber 535 to actuate the piston 530.

A threaded connection is provided at 556 between the upper cap 555 andthe inner mandrel 560 and at 558 between the upper cap 555 and body 510.The upper cap 555 sealingly engages the body 510 at 505, and sealinglyengages the inner mandrel 560 at 562 and 564. A wrench slot 554 isprovided between the upper cap 555 and the spring retainer 550, whichprovides room for a wrench to be inserted to adjust the position of thespring retainer 550 in the body 510. Spring retainer 550 connects at 551via threads to the body 510. Towards the lower end of the springretainer 550, a bore 552 is provided through which a bar can be placedto prevent rotation of the spring retainer 550 during assembly. Forsafety purposes, a spring cover 542 is bolted at 546 to the stop ring544. The spring cover 542 prevents personnel from incurring injuryduring assembly and testing of the tool 500.

The moveable arms 520 include pads 522, 524, and 526 with structures700, 800 that engage the borehole when the arms 520 are expandedoutwardly to the expanded position of the tool 500 shown in FIG. 5.Below the arms 520, the piston 530 sealingly engages the inner mandrel560 at 566, and sealingly engages the body 510 at 534. The lower cap 580is threadingly connected to the body and to the lower retainer 590 at582, 584, respectively. A sealing engagement is also provided at 586between the lower cap 580 and the body 510. The lower cap 580 provides astop for the piston 530 to control the collapsed diameter of the tool500.

Several components are provided for assembly rather than for functionalpurposes. For example, the drive ring 570 is coupled to the piston 530,and then the drive ring block 572 is boltingly connected at 574 toprevent the drive ring 570 and the piston 530 from translating axiallyrelative to one another. The drive ring block 572, therefore, provides alocking connection between the drive ring 570 and the piston 530.

FIG. 5 depicts the tool 500 with the moveable arms 520 in the maximumexpanded position, extending radially outwardly from the body 510. Oncethe tool 500 is in the borehole, it is only expandable to one position.Therefore, the tool 500 has two operational positions—namely a collapsedposition as shown in FIG. 4 or an expanded position as shown in FIG. 5.However, the spring retainer 550, which is a threaded sleeve, can beadjusted at the surface to limit the full diameter expansion of arms520. The spring retainer 550 compresses the biasing spring 540 when thetool 500 is collapsed, and the position of the spring retainer 550determines the amount of expansion of the arms 520. The spring retainer550 is adjusted by a wrench in the wrench slot 554 that rotates thespring retainer 550 axially downwardly or upwardly with respect to thebody 510 at threads 551. The upper cap 555 is also a threaded componentthat locks the spring retainer 550 once it has been positioned.Accordingly, one advantage of the present tool is the ability to adjustat the surface the expanded diameter of the tool 500. Unlikeconventional underreamer tools, this adjustment can be made withoutreplacing any components of the tool 500.

In the expanded position shown in FIG. 5, the arms 520 will eitherunderream the borehole or stabilize the drilling assembly, dependingupon how the pads 522, 524 and 526 are configured. In the configurationof FIGS. 5, cutting structures 700 on pads 526 would underream theborehole. Wear buttons 800 on pads 522 and 524 would provide gaugeprotection as the underreaming progresses. Hydraulic force causes thearms 520 to expand outwardly to the position shown in FIG. 5 due to thedifferential pressure of the drilling fluid between the flowbore 508 andthe annulus 22.

The drilling fluid flows along path 605, through ports 595 in the lowerretainer 590, along path 610 into the piston chamber 535. Thedifferential pressure between the fluid in the flowbore 508 and thefluid in the borehole annulus 22 surrounding tool 500 causes the piston530 to move axially upwardly from the position shown in FIG. 4 to theposition shown in FIG. 5. A small amount of flow can move through thepiston chamber 535 and through nozzles 575 to the annulus 22 as the tool500 starts to expand. As the piston 530 moves axially upwardly in pocketrecesses 516, the piston 530 engages the drive ring 570, thereby causingthe drive ring 570 to move axially upwardly against the moveable arms520. The arms 520 will move axially upwardly in pocket recesses 516 andalso radially outwardly as the arms 520 travel in channels 518 disposedin the body 510. In the expanded position, the flow continues alongpaths 605, 610 and out into the annulus 22 Through nozzles 575. Becausethe nozzles 575 are part of the drive ring 570, they move axially withthe arms 520. Accordingly, these nozzles 575 are optimally positioned tocontinuously provide cleaning and cooling to the cutting structures 700disposed on surface 526 as fluid exits to the annulus 22 along flow path620.

The underreamer tool 500 of the one embodiment of the present inventionsolves the problems experienced with bi-center bits and winged reamersbecause it is designed to remain concentrically disposed within theborehole. In particular, the tool 500 of the present inventionpreferably includes three extendable arms 520 spaced apartcircumferentially at the same axial location on the tool 510. In oneembodiment, the circumferential spacing would be 120° apart. This threearm design provides a full gauge underreaming tool 500 that remainscentralized in the borehole at all times.

Embodiments of the present invention may provide hydraulic indication atthe surface, thereby informing the operator whether the tool is in thecontracted position shown in FIG. 4, or the expanded position shown inFIG. 5. Namely, in the contracted position, the flow area within pistonchamber 535 is smaller than the flow area within piston chamber 535 whenthe tool 500 is in the expanded position shown in FIG. 5. Therefore, inthe expanded position, the flow area in chamber 535 is larger, providinga greater flow area between the flowbore 508 and the wellbore annulus22. In response, pressure at the surface will decrease as compared tothe pressure at the surface when the tool 500 is contracted. Thisdecrease in pressure indicates that the tool 500 is expanded.

FIGS. 6-10 provide more detail regarding the moveable arms 520 and drivering 570 of FIGS. 4 and 5. FIG. 6 shows a “blank” arm 520 with nocutting structures or stabilizing structures attached to pads 522, 524,526. The arm 520 is shown in isometric view to depict a top surface 521,a bottom surface 527, a front surface 665, a back surface 660, and aside surface 528. The top surface 521 and the bottom surface 527 arepreferably angled, as described in more detail below. The arm 520preferably includes two upper pads 522, one middle pad 524, and twolower pads 526 disposed on the front surface 665 of the arm 520. The arm520 also includes extensions 650 disposed along each side 528 of arm520. The extensions 650 preferably extend upwardly at an angle from thebottom 527 of the arm 520 towards pads 522, 524 and 526. The extensions650 protrude outwardly from the arm 520 to fit within correspondingchannels 518 in the pocket recess 516 of the tool body 510, as shown inFIGS. 4 and 5. The interconnection between the arm extensions 650 andthe body channels 518 increases the surface area of contact between themoveable arms 520 and the tool body 510, thereby providing a more robustexpandable tool 500 as compared to prior art tools. The arm 520 depictedin FIG. 6 is a blank version of either an underreamer cutting arm or astabilizer arm. By changing the structures disposed on pads 522, 524 and526, the tool 500 is converted from an underreamer to a stabilizer orvice versa, or to a combination underreamer/stabilizer.

Referring now to FIGS. 7, 8 and 9, an exemplary arm 520 is shown thatincludes two sets of cutting structures 700, 710. FIG. 7 depicts the arm520 from a top perspective, FIG. 8 provides an elevational side view,and FIG. 9 shows an isometric perspective. The top surface 521 and thebottom surface 527 of the arm 520 are preferably angled in the samedirection as best shown in FIG. 7. These surfaces 521, 527 are designedto prevent the arm 520 from vibrating when pads 522, 524 and 526 engagethe borehole. Namely, when pads 522, 524 and 526 engage the borehole,the arms 520 are held in compression by the piston 530. The angled topsurface 521 and the angled bottom surface 527 bias the arms 520 to thetrailing side of the pocket recesses 516 to minimize vibration.

In the top view of FIG. 7, pads 522 comprise cutting structures 710 suchthat the arm 520 provides back reaming capabilities. Back reaming ispulling the tool 500 upwardly in the borehole while underreaming. Pad524 is preferably covered with wear buttons 800 that provide astabilizing and gauge protection function. Pads 526 comprise cuttingstructures 700 for underreaming. In the side view of FIG. 8, theextensions 650 that fit within channels 518 of the body 510 are shownextending upwardly at an angle along the side 528 from the back surface660 of the arm 520 towards pads 522, 524 and 526. FIG. 9 shows the samearm 520 in isometric view.

To change the arm 520 shown in FIGS. 7, 8, and 9 from a back reaming andunderreaming arm to simply an underreaming arm, the back reaming cuttingstructures 710 would be replaced with wear buttons, such as buttons 800.This configuration would result in the underreaming arm 520 shown inFIGS. 4 and 5. Modifying the tool 500 from an underreamer to astabilizer simply requires providing stabilizing structures on all ofthe pads 522, 524 and 526. As a stabilizer, surfaces 522, 524, and 526would be covered with a dense plurality of wear buttons 800 without anycutting structures. The material for the wear buttons 800 may be, forexample, a tungsten carbide or diamond material, which provides goodwear capabilities. In an alternative embodiment, the pads 522, 524, and526 may be coated with a hardened material called TCI 300H hardfacing.

Accordingly, the pads 522, 524, 526 could comprise a variety ofstructures and configurations utilizing a variety of differentmaterials. When the tool is used in an underreaming function, a varietyof different cutting structures 700 could be provided on surfaces 526,depending upon the formation characteristics. Preferably, the cuttingstructures 700, 710 for underreaming and back reaming, respectively, arespecially designed for the particular cutting function. More preferably,the cutting structures 700, 710 comprise the cutting structuresdisclosed and claimed in co-pending U.S. patent application Ser. No.09/924,961, filed Aug. 8, 2001, entitled “Advanced Expandable ReamingTool,” assigned to Smith International, Inc., which is herebyincorporated herein by reference.

Referring now to FIG. 10, additional advantages of one or moreembodiments of the present invention are provided by the one or morenozzles 575 disposed in the drive ring 570. The underreamer/stabilizerpreferably includes three moveable arms 520 spaced apartcircumferentially at the same axial location along the tool body 510. Inone embodiment, the three moveable arms 520 are spaced 120°circumferentially. This arrangement of the arms 520 is preferred tocentralize the tool 500 in the borehole. The drive ring 570 is moveablewith the arms 520 and preferably includes three extended portions 576spaced 120° circumferentially with angled nozzles 575 therethrough thatare designed to direct drilling fluid to the cutting structures 700 ofthe underreamer at surfaces 526. The boreholes 578 in the extendedportions 576 adjacent nozzles 575 accept bolts 574 to connect the drivering 570 to the drive ring block 572 and piston 530. An aperture 571 isdisposed through the center of the drive ring 570 to enable a connectionto the piston 530. Because the drive ring 570 is connected to the piston530, it moves with the piston 530 to push the moveable arms 520 axiallyupwardly and outwardly along the channels 518 to the expanded position.Accordingly, because drive ring 570 moves with the arms 520, the nozzles575 continuously provide drilling fluid to the cutting structures 700 onthe underreamer surfaces 526. The nozzles 575 are optimally placed tomove with and follow the cutting structures 700 and thereby assure thatthe cutters 700 are properly cleaned and cooled at all times.

FIGS. 11 and 12 depict a second embodiment of the present invention,generally designated as 900, in the collapsed and expanded positions,respectively. Many components of tool 900 are the same as the componentsof embodiment 500, and those components maintain the same referencenumerals. There are, however, several differences. The inner mandrel 560of the first embodiment tool 500 is replaced by a stinger assembly 910,preferably comprising an upper inner mandrel 912, a middle inner mandrel914, and a lower inner mandrel 916. The lower inner mandrel 916 includesports 920 that must align with ports 595 in the lower retainer 590before fluid can enter piston chamber 535 to actuate the piston 530. Asshown in FIG. 11, fluid flows through the flowbore 508 of tool 900,along pathway 605 depicted by the arrows. Because the ports 920 of thelower inner mandrel 916 do not align with the ports 595 of the lowerretainer 590, the fluid continues flowing along path 605, past ports595, down through the tool 900.

The tool 900 is selectively actuated utilizing an actuator (not shown),which aligns the ports 920 with the ports 595 to enable the expandabletool to move from the contracted position shown in FIG. 11 to theexpanded position shown in FIG. 12. Below lower inner mandrel 916, abottom spring 930 is disposed within a bottom spring chamber 935 andheld within the body 510 by a bottom spring retainer 950. Bottom springretainer 950 threadingly connects at 952 to the lower retainer 590. Thespring 930 biases the stinger assembly 910 upwardly such that stinger910 must be forced downwardly by an actuator to overcome the force ofbottom spring 930. By moving the stinger 910 downwardly, the ports 920disposed circumferentially around the bottom of lower inner mandrel 916align with the ports 595 of lower retainer 590 that lead into pistonchamber 535.

FIG. 12 shows the tool 900 in an expanded position. In this position,drilling fluid flows through the flowbore 508, along pathway 605.However, because stinger 910 has been actuated downwardly against theforce of bottom spring 930 by an actuator, the ports 920 in lower innermandrel 916 now align with ports 595 in the lower retainer 590.Therefore, when the drilling fluid proceeds downwardly along flow path605 through the flowbore 508 to reach ports 920, it will flow throughports 920, 595 and into the piston chamber 535 as depicted by flowarrows 610.

Due to the differential pressure between the flowbore 508 and thewellbore annulus 22 surrounding tool 900, the fluid flowing alongpathway 610 will actuate the piston 530 upwardly against the force ofspring 540. The piston 530 will push the drive ring 570, which will pushthe arms 520 axially upwardly and outwardly as the extensions 650 on thearms 520 move along channels 518 in the body 510. Once the fluid flowsthrough the nozzles 575 in the drive ring 570, it exits at an anglealong pathway 620 to cool and clean the cutting structures 700 disposedon surfaces 526 that underream the borehole. Accordingly, the secondembodiment 900 of FIGS. 11 and 12 is capable of being selectivelyactuated. Namely, by engaging the upper surface 975 of stinger 910 withan actuator, the tool 900 can be selectively actuated at the election ofthe operator to align the ports 920 and 595. A suitable actuator is theflow switch described and claimed in U.S. Pat. No. 6,289,999 entitled“Fluid Flow Control Devices and Methods for Selective Actuation ofValves and Hydraulic Drilling Tools,” hereby incorporated herein byreference.

Referring again to FIGS. 11 and 12, typically a gap is provided betweenthe upper end 975 of the stinger 910 and the actuator when the tool isin the collapsed position. That gap length must be maintained to ensurethat actuation occurs only when it is meant to occur. Accordingly, upperinner mandrel 912 may include an adjustment ring portion 918, which isjust a spacer ring that makes up any discrepancies in the area betweenthe upper inner mandrel 912 and the middle inner mandrel 914 such thatthe appropriate gap dimension can be maintained.

As one of ordinary skill in the art will readily appreciate, anyactuating mechanism can be utilized to selectively actuate the tool 900of FIGS. 11 and 12. However, the flow switch provides the advantage ofadditional hydraulic indications to the surface, in addition to thepressure indications provided by the increased flow area in the pistonchamber 535 when the tool 900 is in the expanded position of FIG. 12.Namely, the flow switch includes an uplink pulser capable of providingposition and status information to the surface via mud pulse telemetry.Accordingly, one embodiment comprises the tool 900 of FIGS. 11 and 12,and more preferably comprises the tool 900 in combination with thereferenced flow switch.

In operation, an expandable tool 500 or 900 is lowered through casing inthe collapsed position shown in FIGS. 4 and 11, respectively. The firstembodiment of the tool 500 would then be expanded automatically whendrilling fluid flows through flowbore 508, and the second embodiment ofthe tool 900 would be expanded only after selectively actuating the tool900. Whether the selective actuation feature is present or not, thetools 500, 900 expand due to differential pressure between the flow bore508 and the wellbore annulus 22 acting on the piston 530. Thatdifferential pressure may be in the range of 800 to 1,500 psi.Therefore, differential pressure working across the piston 530 willcause the one or more arms 520 of the tool to move from a collapsed toan expanded position against the force of the biasing spring 540.

Before the drilling assembly is lowered into the borehole, the functionof the present invention as either an underreamer or as a stabilizerwould be determined. Referring again to FIG. 1, one example would be touse either embodiment of the tool 500, 900 in the position ofunderreamer 120, and preferably to use the second embodiment of the tool900 in the position of stabilizer 150. As another example, referring toFIGS. 2 and 3, if a winged reamer 220 or a bi-center bit 320 is usedinstead of an underreamer 120, the second embodiment of the tool 900would preferably be used in the position of stabilizer 150. As anunderreamer, one or more embodiments of the present invention arecapable of underreaming a borehole to a desired diameter. As astabilizer, one or more embodiments of the present invention providedirectional control for the assembly 100, 200, 300 within theunderreamed borehole 25.

Turning to FIG. 13, a moveable arm 820 with a roller structure 162 inaccordance with another embodiment is shown. The moveable arm 820 shownin FIG. 13 is similar in structure to the blank arm shown in FIG. 6. Abody 830 includes extensions 650 formed on the sides and configured tofit within corresponding channels of the tool body, such as theembodiment shown in FIGS. 4 and 5. The body 830 is further configured toaccommodate the roller structure 162 rotatably attached thereto. Theshape of the roller structure 162 may be, for example, cylindrical orfrusto-conical. Cutting structures 163 are distributed azimuthally aboutthe roller structure 162. The cutting structures 163 may be integrallyformed with the roller structure 162 or provided as inserts incorresponding pockets formed in the roller structure 162. If provided asinserts, any suitably hard material may be used, such as, for example,tungsten carbide or diamond material. The cutting structures 163 may be,for example, bullet-shaped. Those having ordinary skill in the art willappreciate that the shape of the cutting structures 163 may vary withoutdeparting from the scope of the present disclosure.

The expandable roller reamer may include a plurality of moveable armsazimuthally spaced around the tool body. To balance the forces on theexpandable roller reamer and better stabilize the drillstring, theplurality of moveable arms may be circumferentially spaced apart aroundthe tool body. For example, in one embodiment, the expandable rollerreamer may include three moveable arms with roller structures spaced120° apart.

In the embodiment shown in FIG. 13, the roller structure 162 is formedas a sleeve disposed on a roller pin 161. A set screw 165 fixes theroller structure 162 relative to the roller pin 161. To attach theroller pin 161 to the moveable arm 820, roller mounts 171 are providedat opposing ends of the roller pin 161 and disposed in correspondingpockets formed in the moveable arm 820. The roller mounts 171 may beattached to the moveable arm 820 using, for example, bolts 172. Bearingassemblies (not shown) may be provided within the roller mounts 171.

The structure of the moveable arm 820 of FIG. 13 may provide severaladvantages. The moveable arm 820 may be configured to be interchangeablewith other moveable arms disclosed herein in order for the same toolbody to be useable for different applications by changing out themoveable arms, which can be performed at a drilling site with readilyavailable tools. Interchangeability of moveable arms also reducesmanufacturing costs by increasing quantities of the tool body. Further,the various types of moveable arms may be manufactured with the commondimensions (e.g. extensions 650) before being finished with specializedfeatures, such as pockets to accommodate the roller pin.

FIGS. 14 a-c, show another embodiment of a roller structure inaccordance with disclosed features. In FIG. 14 b, blades 921, may formthe cutting structure, as opposed to inserts, or other cutting elements.The blades may be formed from a super hard material, such as tungstencarbide, or may be formed from a matrix material, and be impregnatedwith another material, such as diamond. Thus, in one embodiment, theblades 921 are diamond impregnated matrix blades. Those having ordinaryskill in the art will appreciate that a number of other materials may beused as the cutting structure in this fashion. In addition, acombination of inserts, shown at 922, and blades may be used together toform a cutting structure. As with FIG. 13, the structure may be boltedon, or otherwise attached. In addition, wear features 923 may be addedto contact the hole wall for stabilization purposes. These wear features923 may comprise a super hard material, such as tungsten carbide. FIGS.14 a and 14 c show other views of the embodiment.

Although interchangeability is a potential advantage, those havingordinary skill in the art will appreciate that an expandable rollerreamer may provide other advantages associated with stabilizing thedrillstring. For example, the expandable roller reamer may be deployedabove another expandable reamer on the drillstring. The outer diameterof the expandable roller reamer can be configured to substantially matchor slightly exceed the outer diameter of the expandable reamer. By sodoing, the expandable roller reamer is able to smooth the wellbore andprovide active stabilization of the drillstring during drillingoperations. While contacting the wall of the wellbore, the rollerstructures freely roll rather than drag, thereby reducing torque on thedrillstring. Further, the diameter of the expandable roller reamer maybe reduced to later pull the drillstring from the wellbore, therebyreducing the risk of the drillstring being stuck in the wellbore.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

1. An expandable downhole tool for use in a drilling assembly positionedwithin a wellbore, the expandable downhole tool comprising: a tool bodycomprising an axial flowbore extending therethrough; and a moveable armcomprising a roller structure comprising cutters and rotatably mountedon the moveable arm, wherein the moveable arm is configured to moveoutwardly in response to actuation of the expandable downhole tool. 2.The expandable downhole tool of claim 1, wherein the tubular bodycomprises a plurality of angled channels formed within a pocket of thetool body and configured to receive corresponding angled extensionsformed on the moveable arm, and wherein the moveable arm translatesalong the plurality of angled channels.
 3. The expandable downhole toolof claim 1, wherein the moveable arm comprises a roller pin on which theroller structure is rotatably fixed.
 4. The expandable downhole tool ofclaim 3, wherein the moveable arm comprises two roller mounts configuredto hold opposing ends of the roller pin onto the moveable arm.
 5. Theexpandable downhole tool of claim 1, wherein the actuation of theexpandable downhole tool occurs in response to differential pressurebetween the axial flowbore and the wellbore.
 6. The expandable downholetool of claim 1, wherein the cutters are inserts.
 7. The expandabledownhole tool of claim 1, wherein the expandable downhole tool isselectively actuatable to allow or prevent a fluid flowing through thetubular body to translate the at least one moveable arm between acollapsed position and an expanded position.
 8. The expandable downholetool of claim 7, further comprising a selectively actuatable sleeve thatprevents or allows a differential pressure to translate the at least onemoveable arm between a collapsed position and an expanded position. 9.The expandable downhole tool of claim 1, wherein the expandable downholetool comprises a plurality of moveable arms.
 10. The expandable downholetool of claim 9, wherein plurality of moveable arms is spacedcircumferentially apart around the tool body.
 11. A moveable arm for anexpandable downhole tool, the moveable arm comprising: a body; a rollerstructure comprising cutters and rotatably mounted on the body, whereinthe moveable arm is configured be moveably received into a tool body ofthe expandable downhole tool.
 12. The moveable arm of claim 11, whereinthe body comprises angled extensions corresponding to angled channelsformed in the tool body.
 13. The moveable arm of claim 11, furthercomprising: a roller pin on which the roller structure is rotatablyfixed.
 14. The moveable arm of claim 13, further comprising: two rollermounts configured to hold opposing ends of the roller pin onto the body.15. The moveable arm of claim 11, wherein the cutters are inserts.
 16. Amethod of underreaming a wellbore to form an enlarged borehole,comprising: using a drill bit to drill the wellbore; disposing anexpandable underreamer above the drill bit; using the expandableunderreamer to enlarge the borehole; disposing an expandable rollerreamer above the first expandable underreamer, wherein the expandableroller reamer comprises a moveable arm comprising a roller structurecomprising cutters and rotatably mounted on the moveable arm; andactuating the expandable roller reamer such that the cutters disposed onthe roller structure contact the enlarged borehole.